Conversion of hydrocarbons



A PZ

H. O. FOLKINS CONVERSION OF HYDROCARBONS Apr-i130, 1946.

Filed March 15, 1944 fl-BUTANE DECOMPOSITION AT 525 C o|2 a45s1as|ou|2|aTIME (MINUTES) INVENTOR.

Hillts OJ'olkifis HEM/ 7 ATTORNEY Patented Apr. 30, 1946 Hillis 0.Folkins, Skokie, m, assignor to The Pure Oil Company, Chicago, 111., acorporation of Ohio ' Application March 15, 1944, Serial No. 526,538

6 Claims.

This invention relates to conversion of hydrocarbons and is moreparticularly concerned with a method for converting higher boilinghydrocarbons into lower boiling hydrocarbons and for making unsaturatedhydrocarbons from saturated hydrocarbons.

I have discovered that if thermal conversion of hydrocarbons is carriedout in the presence of a mixture of a phosphorous oxyhalide and oxygenor gas containing free oxygen, such as air, cracking of the hydrocarbonsis greatly accelerated so 7 that it is possible to obtain larger yieldsof cracked hydrocarbons under the same time-temperaturepressureconditions than it is possible to obtain I by thermal cracking of thehydrocarbons without sensitizer, and it is possible to obtain yields atlower temperatures which are commensurate with yields obtainable athigher temperatures without sensltizers. My invention is applicable toeither batch or cont nuou methods of cracking; In continuous crackingmethods by operating under usual thermal cracking conditions in thepresence of the sensitizer mixture, not only can increased yields beobtained, but higher octane gasoline can be produced. By using thesensitizer mixture, a larger throughput of charging stock for a givensize unit can be effected because of the acceleration in the crackingreaction.

An object of my invention is to provide a method tor conversion ofhydrocarbons.

Another object of my invention is to provide a method for acceleratingcracking of hydrocarbons.

, lation of undesirably large amounts of the sensi-' phorus oxybromide,phosphorus oxybromide dichloride, phosphorus oxydibromide fchloride;

phosphorus oxyfluoride and phosphorus oxyiodide. The phosphorusoxyhalide and the oxygen-containing gas may be mixed with thehydrocarbon prior to charging them to the reaction zone or they may beinjected directly into the reaction zone. The total sensitizer mixturemay be used in concentrations from approximately 0.5 mole percent to 6mole percent'based on the total charge and should not contain less thanabout .25 mole percent of the phosphorus oxyhalideor of oxygen.Higherconcentrations of sensitizers may be used, but within the limitsabove set forth the reaction progresses satisfactorily withoutcausingaccumutizers and their decomposition products in the version of,liquid hydrocarbons such as heargy naphtha, kerosine and gas oil. Acombination of the phosphorus oxyhalide and the oxygen-con- Stillanother object of my invention is to pro .parent from the followingdescription and the accompanying drawing of which thesingle figure is agraphical representation of data showing the unexpected result obtainedunder certain conditions using sensitizer in accordance with my in-.

vention. a

In accordance with my inventionv a small amount of phosphorus oxyhalideand oxygen or gas containing free oxygen, such as air, is mixed with thehydrocarbons subjected to decomposition. As phosporus oxyhalides whichare useful, may be mentioned phosphorus oxychloride, phostainlng gasaccelerates the cracking reaction to an extent in excess of that .whichwould be expected from the cumulative effect of the phosphorus oxyhalideand the oxygen when each is used alone. In order to demonstrate thisfact 'a' number of runs were made using normal butaneot 99% purity ascharging stock. The runs were all made in a Pyrex glass reaction vesselat temperasure below 0.001 mm. of mercury. Sufficient butane inadmixture with the desired amount or approximated atmospheric pressure.

sensitizer composition was then charged 'to'the evacuated vessel untilthe pressure-in the vessel The reaction was permitted to proceed in theclosed reaction vessel while the temperature was main.- tained at 525 C.until a pressure increase of 25 percent above the initial pressure wasobserved, whereupon the reaction gases were removed from i the reactorand analyzed.

Aenumber of runs were alsomade without any sensitizer and runs were madeusing only phosphorus oxychloride and only oxygen as sensitizer.

' beginning of the run until 6 from that point readings were made at v2based on the recorded data forpressure readings obtained as justdescribed. The'flgures in'the table for time required for 25% pressureincrease represent recorded data. g

The sensitization-factors recorded in the tables are obtained bydividing the time required for a particular .pressure increase withoutsensitizer by the time required for the same pressure increase wereplotted with time in minutes as abscissae and percent pressure increaseas ordinates.

Referring to the drawing, curve I is the curve 1 for the average 01'blank runs to 299-3, 305-3 and 309-13. Curve .2 is the curve for run148-13 using 1.0% of oxygen as sensitizer; Curve 3 is the curve for run306-B'using 1.0% phosphorus oxychloride as sensitizer. Curve 4represents the hypothetical or cumulative results. which would beexpected from using 1.0% phosphorus oxychloride and 1.0% oxygen, andcurve 5 is the curve for run. 310-3 in which 1.0% of phosphorusoxychloride and 1.0% of oxygen were used.

Curve 4 is obtained by adding the pressure increase without sensitizerat any selected time (curve I), the pressure increase caused at the sametime by the presence of oxygen alone (curv 2 minus curve I) and thepressure increase caused at the same time by the presence of phosphorusoxychloride along (curve 3 minus curve I) and plotting on the graph theresulting with sensitizer. sum for a sufllcient number of time periodsto Tut: I I

.n-Butane decomposition at 525' C.

- Time mlns.) 10: AP- Sensitization p mum! Sensiticer 7 (values I newPr0ducta,molep0r cent 88-- RunNo. (cml.

cac 1 1 Name Mole,% 5% 12.5% 5% 12.5% 25% Acids Unsats. CO H; .Residue aQ a 10.05 None 2.00 1.01 20.02 0.1 22.5 01; 0.5 11.0

10.00 1.0 2.15 1.05 11.03 1.0 1.1 1.2 0.0 22.1 0.1 1.5 15.1 11.50 2.02.00 0.40 15.05 1.0 1.2 1.4 0.0 25.0 0.1 1.2 15.1 00.50 {g 0.50 2.001005 0.0 2.1 2.0 0.0 22.0 0.1 0.5 10.0 13.45 kg 0.15 2.50 11.15 13.1 3.01.0 0.0 23.4 1.1 1.3 14.2 1005 i3 000 5100 11.50 0.8 2.1: 1.5 0.0 21.300 0.0 10.1

5% values inaccurate 5... to rapid 01111 1 550.

"By referring to Table 1. it will be seen that both oxygen andphosphorus oxychloride alone accelerate the decomposition of butane.Whereas between twenty and twenty-one minutes were required to obtain a25% increase with no sensitize r, 1.0% of oxygen caused a 25% pressureincrease in 18.85 minutes and 2.0% caused a 25% pressure increase in14.70 minutes. 1.0% of phosphorus oxychloride caused a 25% pressureincrease in. 17.83 minutes and 2.0% phosphorus oxychloride caused a 25%pressure increase in 15.05minutes.

On'the other hand, a mixture of 1.0% of phosphorus oxychloride and 1.0%oxygen brought a 25% pressure increase in 10.65 minutes; 1.0% ofphosphorus oxychloride and 2.0% of oxygen caused a 25% pressure increasein 11.15 minutes; and 2.0% phosphorus oxychloride and 1.0% of oxygencaused a,25% pressure increase'in 11.30 p

minutes. 1.0% of oxygen mixed with-1.0% phosphorus oxychloride was beterthan either-2.0%

' of phosphorus oxychloride or oxygen alone.

In order to demonstrate that the increase in acceleration of thereaction is ter h n the additive, or cumulative efiebt of thesensitizers, curvesw ere plotted for the various runs based otherpressure increases recorded at the aforesaid time intervals duringeach run and the curves time the pressure increase for oxygen is 17.0%

minus 15.2 or 1.8%.

(obtained from curve 2) and the pressure increase for phosphorusoxychloride alone is 16.3 (obtained from curve 3). The pressure increase-due to the presence of oxygen is, therefore, 1'7

therefore 16.3 minus 15.2 or 1.1%. The cumulative' pressure increasethatmight have been expected from the combination'of phosphorusoxychloride and oxygen at the time of 10 minutes after the run began isthe sum of the pressure increase at the same time without sensitizer andthe pressure increases'caused by each of the sensitizers,' or 15.2 plus1.8' plus 1.1 or 18.1 percent pressure increase. By referring to. curve4 it will be seen that thispressure increase has been plotted for thetime of 10 minutes.

Comparing this with the experimental. result obtained it will be seenthat only 5.9 minutes were required to obtain a pressure increase or18.1%.- Thus, the reaction is accelerated about seventy percent overwhat would have been expected from the cumulative-effects with oxygenand phosphorus oxychioride alone.

v The pressure increase due 1 to the presence of phosphorus oxychlorideis v asearn 1 The expected timesfor 25% Pressure increase and theexperimental:values obtained a well as the sensitization factorsobtained experimentally and those which represent the additive effect ofthe phosphorus oxychloride and oxygen are given in Table II for runs310-3, 311-1; and 312-3.

TABL: III

n-Butane decomposition with phosphorus oxy- It will be seen thatthe-greatest increase in sensitization factor was obtained when 1.0% ofphosphorus oxychloride and 1.0% of oxygen were used, but in every case abetter sensitization factor was obtained than the expected additive orcumulative result.

The usual eflect of the mixture of phosphorus oxyhalide and oxygencontaining gas is further emphasized by the opposite effect obtainedwhen using a mixture of phosphorus trichloride and oxygen. A run madewith 1.0% phosphorus trichloride alone under the same conditions used inthe runs, data for which is tabulated in Table I, required 10.73 minutesfor 25% pressure increase, whereas in a run made with a mixture of 1.0%oi. oxygen and 1.0% of phosphorus trichloride, 11.27 minutes wererequired for a. 25% pressure increase. Thus, the admixture of oxygenwith phosphorus trichloride lowered the sensitization factor or thephosphorus trichloride instead of increasing it as in the case ofphosphorus oxychloride. 7

It will be apparent from the analysis of reaction products given inTable I that the reaction is primarily one of splitting of the carbon tocarbon bond as shown by the relatively large amount peratures betweenapproximately 375 and 750 C. r

of unsaturated hydrocarbon formed and the relatively small amount ofhydrogen formed. The nature of the reaction products is essentially thesame regardless of whether or not sensitizer is used.

The invention is useful in connection with known types of mineral oil,thermal cracking without catalyst. It is also useful in catalyticcracking operations wherein a solid comminuted catalyst, such as naturalor synthetic aluminasilica compositions, is used. Invention may also beused in connection with cracking of gases to make unsaturatedhydrocarbons, such as cracking of propane to ethylene, cracking ofbutane to ethylene and propylene as well as the crackin of liquidhydrocarbons to olefins or di-oleflns such as butadiene.

I claim:

1. The method of converting hydrocarbons which comprises subjecting saidhydrocarbons to suitable cracking conditions of time, temperature andpressure in the'presence of a total of approximately 0.5 to 6 molepercent of oxygen and a phosphorus oxychloride.

2. Method in accordance with claim 1 in which the oxygen and thephosphorus oxychloride are each present in an amount of at least 0.25mole percent.

3. Method in accordance with claim 1 in which the oxygen and phosphorusoxychloride are each present in an amount between 0.25 and 3 molepercent.

4. The method of cracking hydrocarbons having more than 2 carbon atomsper molecule consisting in subjecting said hydrocarbons to temin thepresence of oxygen and phosphorus oxychloride in amounts not less than0.25 mole percent of each.

5. Method in accordance with claim 4 in which the hydrocarbons contain asubstantial amount of propane.

6. The method of cracking butane which comprises subjecting the butaneto a temperature of approximately 525 C. in the presence of from 1 to 2mole percent of oxygen and l to 2 mole percent of phosphorusoxychloride.

HILLIS O. FOLKINS.

